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Sunday, November 30, 2008

In a previous post (http://futureplanets.blogspot.com/2008/11/warring-views-on-msl.html) I printed excerpts from letters on the problems that MSL is facing. NASA is working to keep the launch of this mission on track for 2009. There will be budget hits -- still unspecified -- to other programs in NASA's science program. I am sure that NASA will structure the hits to minimize the overall pain, but there an expectation of pain to come.

Alan Stern, former NASA Associate Administrator for the Science Mission Directorate has written a reply to Dr. Garvin's reply to Stern's original letter. The reply is printed in the subscription only publication Space News. A core issue in all the letters is whether the Mars Science Laboratory represents a major increase in cost over what the community of scientists expected when they recommended it as a high priority.

NASA has several scientific bodies it uses to get recommendations on its scientific programs. Some, such as the Mars Exploration Program Analysis Group (MEPAG) are on-going. Some, such as the Decadal Survey met for a period at the beginning of the decade to review the overall program and then disbanded. Ultimately, however, NASA as a government agency, has the ultimate responsibility and authority to decide which advice to accept and which to reject. That said, my observation is that NASA listens to these bodies and tries within its budgets to follow the advice (and the sum of the recommendations always seem to call for more missions than there are dollars).

So what advice was NASA receiving regarding MSL in the early to mid parts of the decade? The Decadal Survey (2003 report), which looked at the entire planetary program, made MSL a priority but with the expectation that the cost would be ~$650M (a medium-sized mission). The goals of the mission were limited: "The MSL mission may be important, indeed essential, as a technology-demonstration precursor mission to MSR [Mars Sample Return], but the panel saw little science for MSL that cannot be done as well or better by [ohter] missions [such as Mars sample return]. The detailed examination and analysis of rock samples can be done far more capably in terrestrial laboratories (though admittedly MSL could perform simpler analyses of a larger and more dispersed set of samples than those that an MSR mission could return)... Since the panel’s task was to prioritize science missions and since it sees MSL largely as a technology demonstration mission, it has not included MSL among the prioritized missions."

MEPAG, on the other hand in a 2002-2003 report saw the MSL as a very capable science mission: "MSL will investigate the carbon chemistry in near-surface rocks and soil and provide a rigorous and definitive examination of their mineralogy as well as the extent to which they were formed or altered by water. Later missions in this Pathway will build upon this foundation of investigations and provide much more definitive tests for evidence of past life than will be possible from MSL and earlier landed missions. Advanced in situ instruments are expected to conduct biomolecular chemical analysis and higher spatial resolution examination of samples. The technology to acquire difficult-to-access samples, such as those buried several to tens of meters below the surface, will also be developed."

Both review bodies saw Mars as being the focus of at least one flagship class ($1-2B) missions in the period of ~2009-2020. The Decade Survey assumed it would be a Mars Sample Return (ball parked at $1.5B) and MEPAG saw it as MSL (and several less defined follow-on large missions). NASA decided that MSL was to be a highly capable science mission focused on exploring a site for past habitability and possible chemical signs of post life. The initial cost estimate for this mission after its detailed definition (after both the reports quoted above) was ~$1.5B. It's interesting to note that ESA's ExoMars rover was initially scoped as a ~650M euro mission that has grown to ~1.2B euro mission as it too focused on assessing habitability. (MSL now is probably ~$2.3B, but it is a much more capable rover with precision landing capability.)

NASA's science budget for planetary exploration is largely fixed with some variation from year to year. Fitting a highly capable MSL mission into that budget has to come at the cost of developing other missions to other targets. Is this a case of the Mars science community hijacking the planetary budget? Mars has been the recommended focus of NASA's planetary program for a long period. You can view NASA's planetary program as Mars-focused with funding for a limited number of other solar system missions, or as a balanced program badly out of balance as Mars dominates the budget. It probably depends on whether or not your scientific research focuses on Mars.

What follows are a portion Dr. Stern's views from his reply to Dr. Garvin apropos to the discussion above:

"Dr. Garvin claims that MSL’s original $650M cost, assigned by the NRC’s Planetary Decadal Survey when it ranked the mission high enough to proceed in 2003, was naïve. I agree here: any mildly experienced scientific program manager could have recognized this fact. Yet neither NASA headquarters, nor the implementing NASA center (JPL), nor the Mars community, came forward then, pointing out this obvious disconnect. As a result, the NRC’s community based Planetary Decadal Survey ranked MSL highly at an advertised cost level of $650M. Had they known its ultimate cost would be in excess of triple that, and the consequent damage that would result to the rest of the US planetary program to fund such increases in a fixed-budget environment, I believe it is doubtful that MSL would have received the same high ranking. NASA, JPL, and the Mars community abused the NRC’s high recommendation for MSL by “running away” with the mission’s ambitions and cost after it received a high ranking at the $650M level. When retailers practice such predatory practices, it is called “bait and switch.”

"MSL is a fine scientific mission, and I hope it works, for the fate of the US Mars program lies at its feet. But MSL has caused a great deal of damage to NASA’s broader planetary program: all that remains in hardware development are just one lunar and one outer planet mission; and by NASA’s own recent reckoning, even those two missions and portions of the planetary research and analysis programs which produce scientific discoveries are endangered now by MSL’s spiraling cost."

Saturday, November 29, 2008

Space.com has a long article on the results of the European government meeting that set out forthcoming European Space Agency (ESA) budgets: http://www.space.com/spacenews/spacenews_summary.html

Highlights:

- Core science budget will get 3.5% annual increase, which is not expected to keep up with inflation. Impact on ESA's ability to launch future science missions depends on the actual inflation rate.- Replacement copies of the Kopernikus/Sentinel Earth observation satellites will be built, ensuring continuous measurements as the initial satellites in the system age. This is very big news for the Earth observation community.- Preliminary approval was given to an expanded ExoMars mission. ESA is looking to fund 850M euros with another 200M euros needed from international partners such as Russia or the United States. This apparently will require some scaling back of the current 1.2B euro plan.

First, here are the latest public information as to the full cost of MSL. From a Science article on 9/25/08: "The science laboratory, currently slated for launch in the fall of 2009, is four times heavier than the current rovers trundling across the planet's surface. It features a plethora of advanced tools and instruments designed to analyze rocks, soil, and atmosphere. But that complexity has led to technical troubles and higher costs. When proposed in 2004, the lab was expected to cost $1.2 billion. By this summer, that price tag had climbed to $1.9 billion, and last week NASA space science chief Edward Weiler warned that "there is another overrun coming." Another NASA official put the latest increase at approximately $300 million."

Here is Stern's view from his letter to Science (10/31/08): "When the National Research Council's Planetary Science Decadal Survey recommended the Mars Science Laboratory (MSL) mission for priority funding, it assigned a cost level of $650 million. This value, rather than $1.4 billion, is the true metric for seeing the deep damage that MSL's profligately overrunning cost--now likely to top $2.1 billion--has inflicted on NASA's Mars and wider planetary science budget. Also, the story focused its overrun discussion on instrument costs. Although certainly part of the problem, instrument cost increases have been considerably smaller than overruns in the rest of MSL's budget, which was severely mismatched to the project's complexity from its inception. This mismatch sowed the most fundamental seeds of MSL's cost problems."

And Garvin's view from today's Science: "Stern also claims that MSL was "assigned" a cost level of $650 million. He fails to mention when and by whom. The $650 million cost was a placeholder assigned to a medium-class Mars rover mission by the National Research Council Solar System Decadal Survey committee in 2002, before NASA had developed a basis of cost estimate for MSL. This served as input to NASA studies from 2000 to 2004 to fully define the MSL mission and culminated in the competitive selection of its science payload in late 2004.

"At that time, the overall mission was baselined at a cost of $1.4 billion, not including several costs associated with the radioisotope power system. Given the experience with the cost of the Mars Exploration Rovers and the increased scientific and technical scope of the MSL mission, the so-called assigned value of $650 million is not credible. Stern's own New Horizons flyby mission to Pluto cost NASA more than $650 million; it is unrealistic to expect that a 700-kg analytical laboratory that must soft-land on Mars and drive around with 100 kg of scientific instruments could possibly cost less than a planetary flyby mission.

"Indeed, MSL's 2 years of intensive surface science operations are difficult to compare to any missions in the $650 million price class given typical science-per-dollar metrics. The established NASA cost to implement MSL as of the time of its confirmation review was $1.55 billion (August 2006), which grew due to NASA-wide issues with thermal protection system materials in 2007 to approximately $1.7 billion. The total cost growth of the MSL mission development since NASA confirmed the mission is typical of other Mars exploration missions successfully flown over the past decade. The cost to fly MSL in 2009 will be less than the cost (in today's dollars) of flying a nonmobile Viking Lander laboratory to Mars, and MSL includes a whole new generation of instruments and mobility."

My take is that the two letters talk past each other. ~$2.1B for a rover of MSL's capability is seems a fair price and money well spent for the science (and joy of exploration) that it will return. However, when the mission was fit into a roadmap of science missions by the Decadal Survey, it was as a $650M mission, which would have represented a modest increase in funding (on a per rover basis) over the MER rovers ($820M (per Wikipedia) for two rovers). The difference between that initial guesstimate and the likely final cost is $1.65B. The important question in my mind is whether or not the Decadal Survey would have included MSL in its roadmap if it has assumed that the true cost was >$2B. For only the cost difference, NASA could have flown 3 Discovery missions, 3 Scout missions, 4 MER rovers, or two New Frontiers missions. The problem appears not to be with the management of the MSL program, which as Garvin points out, has experienced cost increases in line with other Mars programs. The problem is with the way mission costs are estimated for Decadal Survey type exercises. NASA took the priorities of that Survey and retained them after it was clear that the cost estimate used in the Survey was off by over a factor of 2X. MSL went from a medium-class to a flagship-class rover. As I said, MSL will be money well spent for the science it returns. However, the Decadal Surveys will be meaningless exercises if they costs they assume in recommending the pieces of the roadmap are off by such large amounts.

Monday, November 24, 2008

The Juno New Frontiers mission to Jupiter has been officially approved: http://www.jpl.nasa.gov/news/news.cfm?release=2008-222

I'm a big fan of this mission. It will be one of those quiet missions -- not a lot of public pizazz -- that will greatly deepen our understanding of gas giants. This mission will probe Jupiter's interior in multiple ways to determine key ratios of elements, the magnetosphere, and the deep structure. It will also study the upper atmosphere and auroras. There will be wide-angle photos of at least the poles. (I'm hoping they can take pictures of the cloud deck near perijove. Since the orbit carries the craft near the terminator, the clouds near sunset should be spectacular -- if such shots from a spinning craft flying past the planet are technically possible as anything but a smear!). No meaningful photos of moons. Just solid science on a key type of planet.

The Space Review piece calls for a new NASA mission and/or focus to reconnect the agency to today's needs. Stern diagnoses the problem, throws out some high level directions, but doesn't make a strong case for any particular mission.

The New York Times piece calls for NASA to prevent its big, technologically challenging missions from consuming its budget.

My take: NASA is an agency defined by a technological province applied to three distinct missions: keep Americans in space through a manned program, carry out innovative science missions, and design and operate several operational programs related to Earth observation. The unifying theme to NASA, in my opinion, is developing innovative technical solutions, and not a particular service. Therefore, NASA's mission at any particular point in time is defined by those projects that push technical innovation. (I'm ignoring the fairly small portion of the portfolio where NASA applies well understood technical solutions to specific -- and usually smaller -- missions.) For NASA to kill one of the large missions is to kill a portion of is current purpose.

NASA does not need to operate this way. It could have the focus on delivering specific benefits in the most cost effective way with manageable risks. The recently approved lunar GRAIL mission is a great example of this approach. Incrementalism does have its drawbacks: it results in publically less exciting projects (few members of the public will be engaged by GRAIL even though the science is excellent), and it is harder to engage Congress in approving large budgets.

Personally, I believe that this is not an either or proposition. A NASA that cannot fly missions because its budget is eaten by a few missions is not successful. On the other hand, a NASA that never takes the bold steps (and risks) is not the space agency I want.

My prescription for NASA's science program would have several parts:

(1) Emphasize Earth observation. We know our planet's climate is changing. We know that human use of the biota is causing fundamental changes. The public gets it. A space agency with this as a central theme (instead of one goal within its science directorate) would be seen a very relevant.

(2) Define an operational science program whose goal is to apply well proven technology to scientific questions. This is the meat and potatoes of the program for scientific exploration of the Earth and space.

(3) Have a portion of the budget for big missions that employ new science. Recognize from the start that these missions carry with them the risk of cost overruns and technical problems. Do not approve them until significant work has been done to define the solution and develop the technology (in NASA speak, carry them through Phase B study before approval). Make this a level of effort program -- fund this at a constant level and when cost overruns occur, let the schedule slip. Do not rob other programs try to hold the missions in this program on schedule.

Sunday, November 23, 2008

In approximately three months, NASA and ESA will pick the destination of the next flagship mission. The teams preparing the proposals have turned in their reports (PowerPoint presentations at http://www.lpi.usra.edu/opag/nov2008Meeting/agenda.html ). Now it is up to the technical reviewers and agency administrators.

Much of the information that is likely to drive the decision we are not privy to. How mature is the technology? How well defined is the science? Does the proposed budget have adequate resources?

Some of the issues, though, the informed public can speculate on and discuss. What follows is my personal assessment. Your comments and views are very much welcomed. If you have something long, please e-mail me (vkane56@hotmail[dot]com) and I'll post it directly. Otherwise, feel free to use the comments link that appears at the bottom of the post.

Both missions are similar in that their core focus is on moons with ice covered oceans. The Titan Saturn System Mission (TSSM) orbiter has an advantage in that it would provide in situ sampling of two moons by passing through the geysers of Enceladus and dipping into the atmosphere of Titan. The Europa Jupiter System Mission (EJSM) will provide some sampling of the tenuous atmosphere of Europa and a plume of Io, but clearly TSSM has the advantage here. If the Europeans contribute a lander and balloon, then the in situ advantage of TSSM is multiplied many times over. (ESA will not make that decision for another two years after decision to fly to Saturn or Jupiter is made.)

However, the advantage is not all to TSSM in regards to studying large icy worlds. Titan is shrouded by a thick, murky atmosphere that makes it difficult to study the surface. Maps will be made in two colors at moderate resolutions (50 m), but detailed geologic studies will be hampered both by the resolution and the lack of shadows to define topography. Jupiter's moons lack meaningful atmospheres, which means that their surfaces can be studied remotely in great detail both in spatial and spectral resolution. Remember the frustrations of trying to study Mars when all we had were Viking images of moderate resolution and limited spectral coverage? TSSM, as I understand the proposal, is limited to similar resolution at Titan while EJSM will have the spatial and spectral resolution of the Mars Reconnaissance Orbiter. If the balloon portion of TSSM flies, its high resolution images will help, but we don't get to chose where the winds will carry the balloon so we don't get to chose what will be imaged and the number of images will be limited by available relay bandwidth.

EJSM has another advantage. Jupiter possesses three large icy moons that allow comparative studies of the formation and evolution of these worlds. Saturn possesses just one large moon, and much of its geologic history will be difficult to impossible to study because of the extensive surface modifications caused by wind and rain.

In the end, I think it is a wash as whether we learn more about ice-ocean worlds (likely a common type of world that we will be increasingly able to study as we get better at studying planets and moons around other stars) from TSSM or EJSM. Both would revolutionize our understanding, but in different ways.

The crux of the decision based on science return in my mind comes from the nature of the objects. Titan rivals Mars as the most Earth-like body in the solar system. Both Mars and Titan have meaningful atmospheres and substantial reservoirs of liquids (in some epoch less frozen than in others). If we our priority is to understand Earth-like bodies, then TSSM is the mission of choice.

Jupiter's system, on the other hand, provides a nearby example of a gas giant with multiple planet-sized moons. We know that gas giants are common around other stars and can reasonably assume that many have large moons. We still lack an adequate survey of the Jovian system. Galileo's 1970s vintage instruments and tiny bandwidth greatly limited what we could learn. Cassini has provided that survey for the Saturn system, and there's little mention of Saturn system science in TSSM presentations. EJSM would bring our understanding of the Jovian system up to par with that of the Saturn system after Cassini.

So, for me, it comes down to whether to initiate the in-depth exploration of an Earth analog with TSSM or complete the in-depth survey of a gas giant system and do comparative studies of icy moons with EJSM. Both are compelling. I will be happy with either choice.

So I did I vote in the poll on this website? I voted for EJSM. I think that wrapping up the survey of the Jovian system makes sense, and the technology investments of the past two decades are ready to be used.

I want to see Titan explored, and believe that NASA should abandon its Mars focus at the end of the coming decade to refocus those funds on a series of Titan missions. (I don't think the study of Mars will end -- too many nations now have or soon will have the technical capability to take the baton.) For Titan, I think that we should think in terms of a sequence of missions for this world. We first need a long lived orbiter that can act for a decade or more as a relay craft and map the surface of the moon. We need at least three follow up in-situ missions (although they could be combined into one or several launches): a very capable balloon platform to perform atmspheric chemistry and subsurface sounding, a lake lander to sample the disolved organics, and a long-lived lander (or preferably 3) that would provide the network science to study the climate and interior. The key, though, is to have that orbiter in place. Without it, the bandwidth for the balloon and seismic studies is simply too small. Right now, the TSSM orbiter is very large, very capable (if you offer $3B, scientists and engineers will find ways to use it). Perhaps two smaller orbiters that split up the tasks is what we should be aiming for.

My preference for EJSM is that it finishes a task. My problem with TSSM is that it doesn't go far enough, and we should be thinking more long term.

Thursday, November 20, 2008

Over the coming months I (often with the help of Bruce Moomaw) will look at concepts for each of the New Frontiers mission targets. To date, the most popular target for the next mission based on votes from readers has been Venus, so we’ll start with that world.

Here is what the New Frontiers draft announcement of opportunity (AO) states as the goals for a mission to Venus:Although the exploration of the surface and lower atmosphere of Venus provides a major technical challenge, the scientific rewards are major. Venus is Earth’s sister planet, yet its tectonics, volcanism, surface-atmospheric processes, atmospheric dynamics, and chemistry are all remarkably different than on Earth, which has resulted in remarkably different end states for its surface crust and atmosphere. While returning physical samples of its surface and/or atmosphere may not be possible within the New Frontiers cost cap, innovative approaches might achieve the majority of the following objectives: • Understand the physics and chemistry of Venus’ atmosphere through measurement of its composition, especially the abundances of its trace gases, sulfur, light stable isotopes, and noble gas isotopes;• Constrain the coupling of thermochemical, photochemical, and dynamical processes in Venus’ atmosphere and between the surface and atmosphere to understand radiative balance, climate, dynamics, and chemical cycles;• Understand the physics and chemistry of Venus’ crust through analysis of near-IR descent images from below the clouds to the surface and through measurements of elemental abundances and mineralogy from a surface sample;• Understand the properties of Venus’ atmosphere down to the surface through meteorological measurements and improve our understanding of Venus’ zonal cloud level winds through temporal measurements over several Earth days;• Understand the weathering environment of the crust of Venus in the context of the dynamics of the atmosphere of Venus and the composition and texture of its surface materials; and• Map the mineralogy and chemical composition of Venus’ surface on the planetary scale for evidence of past hydrological cycles, oceans, and life and constraints on the evolution of Venus’ atmosphere.Any mission architecture that achieves the majority of the science objectives stated abovefor a cost within the New Frontiers cost cap will be considered responsive to this AO.http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=170829/NF-3_Draft_AO_V8.pdf

The following comes from Bruce Moomaw with [comments from me within braces].

We've talked earlier about the possibility of descoping Kevin Baines "VALOR Plus" Venus concept -- and in this connection I've just remembered a passage from the Space Studies Board's earlier New Frontiers recommendations. On page 35 of the PDF ( http://www.nap.edu/catalog.php?record_id=12175 ), we find:

"The challenges associated with landing in a region not previously sampled, collection of a sample, and lofting to a more clement altitude are the source of greatest technology and cost risk. Consequently, the New Frontiers announcement of opportunity should not preclude a mission that addresses the major goals for chemical sampling of the mid- to lower atmosphere on Venus and characterizing atmospheric dynamics, but lacks a surface sampling component. [Italics theirs.] On the other hand, a mission that only addressed surface sampling would not be acceptable."

...which would seem to be an open invitation to Baines [who has proposed several atmospheric probe and balloon missions] to propose a mission including only the balloons as an absolutely firm component, with their dropsondes and the orbiter as optional.

[Links to several of Baines’ proposals:http://conferences.library.gatech.edu/ippw/index.php/ippw6/1/paper/view/65/85above more recent; below older:http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/13986/1/00-0365.pdfhttp://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18472/1/99-1959.pdfand this one that uses a nuclear power source which is not allowed for this New Frontiers proposalhttp://futureplanets.blogspot.com/2008/11/agu-future-mission-abstracts.html]

As for the dropsondes: their biggest importance might lie in whether they could use multispectral imaging to tell whether they were coming down on a mafic or felsic surface, and thus whether the tesserae (and/or Ishtar Terra) are granite, indicating that Venus had an ocean. I don't know whether they would be capable of doing this, though. [Baines’ proposal shows the dropsondes in a configuration that would drop straight down. If a paraglider parachute was used instead, the dropsondes could image a fairly long traverse. With a 10:1 glide to drop ratio, for example, the dropsondes could cover a traverse of 100 km in the last 10 km of descent. Of course the trade off is extra complexity and mass: a parachute, longer lived batteries, more thermal protection.]

Like most nonscientific fans of planetary exploration, I myself find geology more interesting than atmospheric and magnetospheric science -- all that nice visual stuff. In that connection, I also note that one of the instruments on Baines' orbiter would be a high-resolution radar altimeter -- and this has reminded me of one of the more interesting recent Venus mission concepts: Bruce Campbell's "VISTA" Discovery proposal that would have included a high-resolution radar altimeter and a subsurface radar sounder like the one that had to be dropped from Venus Express: His reasoning is that one of the burning questions about Venus is whether it really did undergo a single episode of near-total resurfacing or not -- and that even in-situ dating of its rocks may leave that question open because the planet is so hot that the substances usually used for such dating (argon, rubidium, etc.) may have escaped from its rocks. A radar sounder, on the other hand, could look into this question by seeing how lava flows are overlaid over each other across the planet's surface. (Note that this is just the sort of instrument they have in mind for the Titan Orbiter, too.)

[In the first New Frontiers competition, a dual lander mission was proposed: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38184/1/03-2520.pdf ]

Esposito has since said (I can't remember where) that he plans to re-submit a modified version of this proposal next time. Apparently the main problem keeping it out of the finalist list last time was an inappropriate launch window. (If I remember correctly, the flyby carrier would have carried one instrument: a German camera.)

Finally, consider the Venus lander concept designed by JPL's summer school interns in 2007:http://drake.contactincontext.org/thad/Presentation/VEIL_final.pdfhttp://drake.contactincontext.org/thad/Presentation/VEIL_agu_2007v3.pdf

This last one is noteworthy because it uses LIBS/Raman for analysis, which neatly avoids both all the rigmarole of a high-teperature/pressure drill/airlock system and can allow a much faster multi-spot analysis. (Alian Wang and R.C. Wiens doing studies on the feaasibility of LIBS/Raman through the Venusian atmosphere, and so far has found no probleml their latest test is at http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm08&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm08%2Ffm08&maxhits=200&="P33A-1438" .)

[Finally, there are options for studying Venus’ geology from orbit. The following abstract was presented 3 years ago.]

AGU Fall 2005 Conference P23E-05TI: Studies of Venus from Orbit - Microwave Remote Sensing after MagellanAU: * Campbell, B AEM: campbellb@si.eduAF: Center for Earth & Planetary Studies, MRC 315, Smithsonian Institution, Washington, DC 20013 United StatesAU: VISTA TeamEM: campbellb@si.eduAB: The Magellan dataset provided the first opportunity for detailed analysis of the geology and geophysics of Venus, revealing that the surface is characterized by three major landform types: upland tessera plateaus, large shield volcanoes, and vast lowland plains assumed to reflect volcanic flooding. Plate tectonics does not appear to be currently active, so heat is released by some combination of conduction through the crust and effusive volcanism. The relative importance of these mechanisms is not well understood. The dense atmosphere filters the small impactors that form the basis of relative age dating among regions on the Moon, Mercury, and Mars. The remaining impactor population is reflected in ~1000 craters larger than ~5 km in diameter, which suggest that the surface is younger than ~1 b.y. Beyond this, the low spatial density of craters precludes definitive relative dating of even regional-scale features. It is also likely that the high surface temperature precludes the use of radioisotope age dating, either in situ or on returned samples. Unlike any other terrestrial planet, Venus therefore offers no simple evidence for differences in relative age or rates of formation between major regions and landforms. This has led to widely varying interpretations of geologic history and atmospheric evolution. For example, it is possible that Venus has undergone an essentially linear progression of geologic processes now recorded at the surface by the tesserae, plains, and volcanic constructs. It has also been suggested that large, episodic releases of heat by effusive volcanism would inject atmospheric volatiles, leading to transient heating of the atmosphere to perhaps 1000 K. The contrasting view is that Venus' surface reflects a progression of processes generally linked to lithospheric thickness, but that this progression may occur at very different times in different places. The choice between these interpretations is crucial to understanding the geologic and climate history of Venus, and the potential range of terrestrial planet evolutionary styles. More than ten years after Magellan, these questions appear to be impossible to answer without a fundamentally new view of the planet. The key to solving the mystery may lie below the Venus plains. Are there buried impact craters or basins, and do these indicate age differences between the major plains regions? Do the tesserae comprise a regional or global basement? Are the plains formed in great lava floods, or by a sequence of thinner flow units? How thick are the plains, and what does this indicate about release of heat by resurfacing? Are the great shield volcanoes always younger than the plains, or do their earlier deposits lie buried by interleaved plains-forming lavas? We present the science rationale for VISTA, a Discovery-class orbital mission to Venus, carrying ground-penetrating radar sounder and high-resolution radar altimeter instruments, to answer these fundamental questions and place the Magellan data in an entirely new context.

Wednesday, November 19, 2008

The press release on the final candidates is at: http://www.jpl.nasa.gov/news/news.cfm?release=2008-219

"The sites, alphabetically, are: Eberswalde, where an ancient river deposited a delta in a possible lake; Gale, with a mountain of stacked layers including clays and sulfates; Holden, a crater containing alluvial fans, flood deposits, possible lake beds and clay-rich deposits; and Mawrth, which shows exposed layers containing at least two types of clay."

Details on each of the candidate sites (and the ones that didn't make the cut) can be found at: http://marsoweb.nas.nasa.gov/landingsites/msl2009/workshops/3rd_workshop/program.html

Tuesday, November 18, 2008

The Mars Science Lab (MSL) should have real name by next spring suggested by a student under 18 in an American school. Dang, my son is 19, so I can't submit my ideas through him. If you aren't so constrained, read the press release at http://www.jpl.nasa.gov/news/news.cfm?release=2008-215

Monday, November 17, 2008

Last time [the New Frontiers price cap] was $700 million in FY 05 dollars. The $650 million cost cap this time does not include the launch vehicle cost. Whatever flies is still going to have to be about the same cost as Juno.

And when it comes to Io or Ganymede missions: we won't know until February whether the Europa Flagship mission will fly to take a look at those worlds, and the New Frontiers mission proposals this time are due in May. Would any team really spend three months planning a mission to such a world with the serious odds that they would then discover (with only three months left to plan a replacement mission) that their mission was redundant?

[The following portions were written before Bruce realized that the cost cap does not include the launch vehicle, which will raise the overall NASA cost of the mission above the last selection's price target. It's not clear how the overall budget compares given inflation (which occurs at a different rate for aerospace than for consumers).]

Consider how comparatively simple Juno is -- spin-stabilized, and even its visible-light camera is optional. And yet there's a good chance it wouldn't have qualified for this round. (For that matter, consider the cost of MAVEN!) It will be a miracle, I think, if they can fit in anything under this cost cap that would be scientifically cost-effective for any of Jupiter's moons, and I would also tend to count out any comet-nucleus sample return and any Mars Network mission (consider the $1.2 billion cost estimate for even the minimum version of that as provided by the Mars Architecture Tiger Team.) A Mars Network mission focused solely on Mars meteorology, that would strew around a bunch of tiny lander capsules (like the Robert Haberle's "PASCAL" concept), might get in under the cost cap -- but would meteorology alone be enough, since planetary internal structure is the real primary goal of the suggested NF network mission, and something that focused just on Martian meteorology would be better described as a Mars Scout?

A solar-powered Trojan/Centaur flyby could also produce problems (especially given the need to shield its solar arrays from coma dust during the Centaur flyby -- maybe they could include an onboard battery capable of lasting long enough to relay back all the data from the Centaur?). An Aitken Basin sample return involving just one lander instead of the two included in the "Moonrise" concept might make it -- but there are uneasy doubts about the odds that one Aitken lander by itself could get the rather specific samples of mantle and impact-melt material that they need. All in all, I'd rate the favorites this time as being either a near-Earth asteroid sample return aimed at a really primitive asteroid of the sort that almost never turns up as meteorites (like the "OSIRIS REx" concept -- maybe aimed at Wilson-Harrington as a cross between an asteroid and a comet?) or a properly-scaled Venus mission (such as a significantly descoped version of Kevin Baines' "VALOR Plus").

[Van's comments: Bruce's comments nail what is likely to be the key focus of the next New Frontiers selection. I expect that the scientific community will display considerable ingenuity in proposing missions that address a portion of the goals for a target. Juno did that by proposing an orbiter that uses remote sensing to fulfill the goals for a mission that originally called for atmospheric entry probes. A descoped Valor Venus mission similarly fulfills the atmospheric goals for the in situ Venus mission. Unfortunately, we'll have to wait almost a year to the first down select to three missions to learn what has been proposed.]

The latest edition of Aviation Week and Space Technology reports that ESA will request only 3.5% budget increase for the science program. This reportedly will impact ESA’s Cosmic Vision program, which consists of a medium class (300M euro) and a large class (650M euro mission) mission to be launched by 2018. If this budget goes forward, the large class mission could not fly before 2020.

If ESA partners with NASA on an outer planet flagship mission, it will be through the large class mission. (NASA has recently pushed its launch target for this mission to ~2020, reportedly to enable it to synch up with ESA funding.)

ESA appears to be on target to secure partnerships with other space agencies that would enable all the currently planned ExoMars mission to launch in 2016.

ESA has a website on the candidate missions for its Cosmic Vision program: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=100

Medium class candidates:- Cross-Scale - quantify the coupling in plasmas between different physical scales- Euclid - Mapping the geometry of the dark Universe - Marco Polo - return a sample from a Near-Earth Object belonging to a primitive class to the Earth- PLATO - PLAnetary Transits and Oscillations of stars for a full statistical analysis of exoplanetary systems- SPICA - probe galaxy, star and planetary system formation, as well as the evolution of dust and gas in the interstellar medium of our own and distant galaxies.

Summarized from http://marsoweb.nas.nasa.gov/landingsites/msl2009/memoranda/msl_landing_site_memo_nov_08.pdf

"On November 5, 2008, representatives of the MSL project management, engineering, and science teams met along with members of the external MSL landing site steering committee and selected review board members to discuss the engineering assessment of landing safety, basic traversability, and the current status of predicted actuator thermal performance, in order to combine this information with the science rankings from the 3rd Community Workshop recommended to the PSG. Based on assessment over thepast months, the project resources and timeline allow only 3 or 4 sites to have the full data acquisition and detailed analyses required for final approval by next spring."

"Therefore the final 4 sites selected for further analysis are:HoldenGaleMawrth (ellipse placement #2)Eberswalde"

Group 1: Holden, Gale, MawrthGroup 2: Eberswalde (risk still fairly low for portions of ellipse surveyed, but potential high slopes androck coverage issues in remainder of ellipse)“Group 2.5”: Nili [with some discussion that the site may be outside the engineering limits altogether]

Sunday, November 16, 2008

Release Date: November 17, 2008
The National Aeronautics and Space Administration (NASA) Science
Mission Directorate is releasing a Draft Announcement of Opportunity
(AO) for community review and comment for the next mission in the New
Frontiers program (NNH09ZDA003J). The science objectives covered by
the Draft New Frontiers AO include South Pole -- Aitken Basin Sample
Return, Venus in Situ Explorer, Comet Surface Sample Return, Network
Science, Trojan/Centaur Reconnaissance, Asteroid Rover/Sample Return,
Io Observer, and Ganymede Observer.
http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=170829/NF-3_Draft_AO_V8.pdf

Note the opportunity to vote for your favorite mission on this blog page.
The rules for the selection are:

o In November 2009, up to three missions will be selected for a 9 to 11 month Phase A that will be funded up to $2.5M each. Down selection to a single mission for flight will occur in January 2011. Launch is to occur no earlier than 2015 and no later than 2018.

o This NF-3 AO will solicit only missions that do not require nuclear sources for power generation or propulsion, although Radioisotope Heating Units (RHUs) and calibration sources will be allowed.

o The Principal Investigator (PI) Mission Cost for all phases of the mission will not include the launch vehicle and will be capped at $650M in FY09 dollars.

o Proposers will be given the option of selecting none or one of two specific technologies for insertion into their mission. The two technologies are the NASA Evolutionary Xenon Thruster (NEXT) and the Advanced Materials Bipropellant Rocket (AMBR) engine. For missions that insert NEXT, the cap on the PI Mission Cost will be raised up to $15M. For missions that insert AMBR, the cap on the PI Mission Cost will be raised up to $5M.

To refresh your memory, New Frontier’s missions are non-Mars (with a possible exception noted below) missions with a price tag of $500M-$1B. (The price envelope changes with each mission.) NASA announces that it will select a mission targeted to a pre-selected group of destinations, and scientists (paired with laboratories such as the Johns Hopkins Applied Physics Lab or JPL or paired with an aerospace company) propose missions. NASA then selects the mission with the best science return given the budget and development risk. The New Horizon’s Pluto mission was the first New Frontiers mission selected and the Juno Jupiter mission the second.

The price cap in particular seems very tight (although the launch is not included). My guess is that this will limit the complexity and development R&D of the missions. I expect that a fairly simple mission will be selected.

NASA preselects a group of target missions from which it selects the winning mission. (Mars has been excluded from previous selections.)

Which mission gets selected is hard to handicap in advance since it requires knowledge of the details of the proposals. Often issues of cost or risk not generally known to the public can be the deciding factor. Several of the targets have mission studies in progress as part of concept studies for the Discovery program but would use Stirling RTG power sources. I would not be surprised to see those proposals adapted for the New Horizons competition but with the use of solar panels.

It is fun to speculate about what you personally would like to see based on the thrill of exploration and expected scientific return. So for the next selection, here is my assessment; it is strictly personal and everyone is encouraged to present their own views:

Asteroid Rover/Sample Return – Returned samples can tell us much more than can a simple orbiter or lander. However, this mission probably has several challenges. The easy to reach near Earth asteroids probably are not the most interesting asteroids, and the main belt asteroids would be very challenging to do for a round trip mission. Grabbing the most scientifically meaningful sample from an asteroid is challenging. Also, laboratories have lots of asteroid samples already in the form of meteorites. Rovers on the small asteroids are technically challenging -- hoppers are easier. Rovers on larger main belt asteroids face the costs of reaching the destination and implementing a descent system.

Comet Surface Sample Return Mission – The New Frontiers competitions generally allow creativity in meeting the goals so an alternative mission that has been proposed to collect the samples from the coma might be an alternative. Here, I think that the diversity of comets and our new knowledge that they may have substantial dust covers makes it questionable whether or not a mission would get meaningful samples of the ice. I think this mission is unlikely to be chosen before the Rosetta comet rendezvous/lander mission tells us a lot more about the surfaces of comets. It would also be very challenging to return cryogenically frozen ice samples in a New Frontier’s budget. The review panels have said that it would be okay to propose a mission that returns melted samples, but the proposers would have to show that such samples would still have scientific merit.

Ganymede Observer/Io Observer – I put these together because they have similar challenges. The challenge for both these missions is to convince review panels that more flybys of these moons is a good way to spend $650M+. Based on past mission studies, an orbiter for Ganymede would not seem to fit within the budget (and is technically impossible for Io given the radiation). Both missions have the challenge of making solar panels work in the radiation belts of Jupiter (a much more severe challenge for an Io mission). I will point out that the two missions could be combined. A craft could initially do a series of Io flybys, raise perijove, and then do a series of Ganymede flybys (or alternatively, a series of Europa flybys) with continuing long range observations of Io and Jupiter. This more complicated mission probably busts the budget, but follow-on flybys of Ganymede might be funded as a Discovery program mission of opportunity. If the Jupiter system is selected as the target for the next flagship outer planets mission, then I don't either of these missions would be selected. If the Saturn system flagship mission is selected, then the appeal of a Jovian system may rise considerably.

Lunar South Pole-Aitken Basin Sample Return Mission – Sample return missions always rank highly in terms of scientific merit. This mission was a finalist for the last competition (losing out to Juno). Why it lost wasn’t clear based on scientific merit. The complexity of landing on the moon, selecting samples that answer the key scientific questions, and then returning to the Earth may have been too great.

Network Science (including Mars) for seismology and meteorological observations distributed across a globe (other observations also possible) – Mars is the obvious candidate. A network science mission is the second highest ranked scientific goal for Mars after a Mars Sample Return. However, this mission has been estimated to have a budget above $1B and it requires an orbiter to provide communications relay (not included in the >$1B estimate). Mars also already receives a substantial portion of NASA’s planetary science budget. My guess is that the next New Frontiers mission will be used to round out the list of targets NASA is exploring. ESA’s ExoMars 2016 mission also will include a single surface station that could teach us a lot about how to tune the instruments and design of a full network.

Trojan/Centaur Reconnaissance – These are an interesting series of targets, but I don’t know if NASA will be willing to use it’s ~2 times a decade chance to fly a New Frontiers mission to do reconnaissance.

Venus in Situ Explorer – A pair of short-lived Venus landers were proposed for the last New Frontiers competition. I’ve heard through the grapevine that the mission wasn’t selected because the timing was wrong to take advantage of alignments of planets for a launch within the budget timeframe. (There may also have been substantial mission cost and implementation risk – Venus’ surface is not a friendly place!) The exploration of Venus’ atmosphere in situ and surface has been ignored (by the next time a New Frontiers mission flies) for decades. Counting against this mission is the fact that the Venus scientific community is pushing for a much more ambitious mission to Venus involving an orbiter, balloons, and more capable landers. A mission using just balloons to explore the atmosphere could be an alternative.

So which missions would I like to see if every one could fit within the dollar and risk budgets? My first choice would be a pair of Venus landers. It simply has been too long since we’ve done in situ Venus science. If not that mission, I’d pick the Io Observer, partially because Io is my second favorite moon (after Titan) and because the mission can do additional Jovian system science (Jupiter meteorological observations, for example).

My choice for the following New Frontiers mission isn’t a competition at all. I’d go with the Argo Jupiter-Saturn-Neptune/Triton-Kuiper belt mission. While it would be flybys to at all destinations, the chance to take modern instruments to Neptune/Triton is compelling as is the opportunity to explore a wider variety of Kuiper belt objects than New Horizons can (post Pluto). Observing changes in the Jupiter and Saturn systems would simply be icing on the proverbial cake.

My guess is that the final selection will go for the mission with the lowest price tag and development risk that meets the minimum bar for scientific return. Don't get me wrong -- such a mission will produce excellent science, but it's public appeal may be limited. I think the selection of the Discovery Grail mission in the last selection is an example of this criteria in operation. Superb science, but not exciting exploration. That, I think, is the price future missions will pay for past successes (all the cheap, exciting exploration missions have been done) and mistakes (the cost overruns on the Mars Science Laboratory, James Webb telescope, Kepler mission, etc.).

Wednesday, November 12, 2008

As far as I can tell, the only change since March is that the plan to fly by a Jovian Trojan has been cut out -- although flying by Jupiter (along with Saturn) also lops a lot off the total mission time (13-15 years to reach a big KBO, instead of 19-21 years, with the launch still being in 2019). They recognize that both the development schedule and the proximity to the New Frontiers upper cost cap are tight.

The flyby of Jupiter would be distant -- well beyond Callisto's orbit -- but the flyby of Saturn would be close enough that they might be able to squeeze in a flyby of Enceladus, for whatever that's worth.

The presentation on the Argo Jupiter/Trojan-Saturn-Neptune+Triton/Kuiper object mission is now available: http://www.lpi.usra.edu/opag/nov2008Meeting/presentations/argo.pdf

Less here on the science than has been presented in the past: http://www.lpi.usra.edu/opag/march_08_meeting/presentations/hammel.pdf

The mission backers are looking for two things at this point. First, a high ranking from the next Decadal Survey of planetary study (and missions) priority. NASA and Congress take the priorities set by these surveys very seriously. A priority for this mission would substantially increase its chances of selection. Second, the proposers want to make sure that key resources are available including plutonium for the power source and the large 70 m Deep Space Network antennas.

On another note, this blog was originally intended as an occasional message board. Postings have been more frequent than expected. I've added buttons so this blog can be more easily followed via RSS. Let me know if you would like me to take you off the mailing list for new posts.

Monday, November 10, 2008

(2) The plan is still for NASA to pick its mission in February, while the ESA wouldn't decide whether to cooperate until the end of 2012 (and would in fact reduce its "L-Mission" choices from 3 to 2 in number only in late 2010). ESA's other two choices are still an ESA collaboration with NASA's "LISA" gravity-wave mission, or with Japan's "XEUS" X-ray astronomy mission. (This implies that there's some feedback between which OP Flagship mission NASA picks and whether it picks LISA, which is a very high-priority astrophysics mission for us.)

(3) Our Europa Orbiter could make Io flybys as low as 75 km to directly sample an eruption plume -- if it retains its onboard mass spectrometer, which is one of its lowest-priority instruments.

(4) The ESA really is apparently serious about a solar-powered Ganymede Orbiter to complement NASA's Europa Orbiter, and with a hefty 73-kg science payload (same presentation). It would spend 13 months making repeated Callisto flybys in 1:1 or 2:3 resonant orbits before turning its attention to Ganymede, where it would end up in a low circular orbit. I think that, once again, ESA's eyes are bigger than its wallet; but who knows?

(5) The ESA's Titan Lander would indeed be a lake floater, which would make a leisurely 6-hour atmospheric descent by parachute (to examine Titan's atmosphere in more detail), and then work for only 3 hours on the lake itself: (They're talking about putting a camera on it, which strikes me as an exercise in futility; but then the camera would only weigh 1 kg.)

(6) They're quite serious about dropping off the Balloon during the main spacecraft's first Titan flyby -- after its Saturn orbit insertion -- and then dropping off the Lake Lander on the next Titan flyby. Although the Balloon's projected lifetime wouldn't be nearly as long as the 2 years the main spacecraft would spend in Saturn orbit before inserting itself into orbit around Titan, the Balloon would have a small gimballed high-gain dish antenna on its gondola that could relay data back to the main craft at 2000 bps even at a distance of 5 million km -- that is, almost wherever the main craft happened to be in the Saturn system. During the Orbiter's close flybys of Titan, the Balloon could relay data at up to 1 million bps.

(7) The Balloon would indeed hang at 10 km altitude, making no attempt to approach the surface and pick up samples -- but ESA is talking about a possible auxiliary small flat "Geosaucer" that would be dropped from its gondola onto Titan's solid surface with a seismometer and magnetometer onboard.

(8) The Titan Orbiter would make a series of 7 Enceladus flybys during a period of a single month -- and, oddly, they are talking about subsurface radar sounding of the plume region, despite the problems that the Titan aerobraking would then cause the radar sounding antenna. I don't know whether this is a glitch in the presentation, but they mention it twice. Maybe the antenna would be retractable?

(9) The baseline plan is for the Titan Flagship to be attached to a SEP stage that would allow it to reach Saturn in 9 years -- without that, it would take 18 months longer to reach Saturn (and its time in orbit around Titan would be clipped from 20 months to 16 months).

As noted in previous posts, OPAG has presented detailed mission summaries for both proposed outer planet flagship missions: the Europa Jupiter System Mission (EJSM) and the Titan Saturn System Mission (TSSM). NASA and ESA will select between the two missions early next year. NASA intends to fly its proposed contribution to the selected mission. ESA’s contribution will be in competition with other proposed large missions, and hence may not fly.

I’ll break my observations into three posts over approximately as many days. Tonight I’ll discuss the EJSM mission (to take the missions in the order in which they were presented).

I’ve now read the EJSM presentation twice, and my simply reaction is, “Wow!” The proposed two spacecraft mission (NASA’s Jupiter Europa Orbiter (JEO) and ESA’s Jupiter Ganymede Orbiter (JGO)) would provide the kind of revolution in our understanding of this system as the three Martian orbiters of the last decade have compared to the Viking orbiters. Both the last Jupiter mission, Galileo, and the Viking orbiters were 1970s technology and instrumentation. The capabilities brought by both the NASA and ESA craft are as advanced compared to Galileo (even if its antenna had worked) as the Mars Reconnaissance Orbiter compared to the Viking orbiters.

In evaluating this proposal, it is important to remember that the two craft explore 6 bodies:

Jupiter itself through extensive observations of the atmosphere from each craft,

Io (3 science flybys with JEO plus remote monitoring by JEO and JGO (if a narrow angle camera is added to the payload)),

Europa (9+ months of study from orbit),

Ganymede (6 JEO flybys plus 6+ months of study from orbiter by JGO)

Callisto (9 JEO flybys plus numerous flybys by JGO)

Jupiter’s magnetosphere

The proposed mission has three themes that transcend the simple exploration of yet another solar system body: Explore Europa and Ganymede as possible abodes of life and examples of “The emergence of habitable worlds around gas giants”; further our understanding of the dynamics of a gas giant (a type of planet that astronomers have found is common in many solar systems) through studies of the atmosphere and magnetosphere; explore the similarities and differences of the Jovian moons as an example of a mini-solar system.

The NASA and ESA craft are presented as a joint mission, as is intended by this proposed cooperative and highly complimentary mission. However, either craft by itself would represent a major mission in its own right that could be justified on its standalone contribution. Should Titan be chosen as the destination of the next flagship mission, the ESA mission is a good example of what a moderate cost (~$1B or somewhat more than NASA’s New Frontiers missions) Jovian mission could do. If Jupiter is the chosen destination but ESA decides not to fly its craft, then the JEO mission could be easily enhanced by extending the time spent doing flybys of Ganymede and Callisto prior to entering Europan orbit.

Jason is the blogger at The Gish Bar Times (I highly recommend the site: http://gishbar.blogspot.com/). He has kindly given permission to reproduce his entry here.

The presentations for last week's OPAG Fall Meeting are now online. These include several presentations covering the two Outer Planet Flagship mission proposals, the Europa/Jupiter System Mission (EJSM) and the Titan/Saturn System Mission (TSSM), as well as other programmatic presentations.

The final reports for the two proposal teams were due last Monday so last week's OPAG meeting were the first opportunity to present the finalized proposals. These include a more detailed sample mission profile, payload, and science goals. EJSM would include two mission components: the Jupiter Europa Orbiter (JEO) and the Jupiter Ganymede Orbiter (JGO). According to the baseline mission plan, the two components would launch separately in February and March 2020. JEO would arrive at Jupiter in December 2025 while JGO would arrive in February 2026. JEO would then conduct an orbital tour of the Jupiter system over a period of 31 months, before entering orbit around Europa in July 2028. During the Jupiter tour phase, JEO would perform more than two dozen flybys of the Galilean satellites. JGO would conduct a more focused tour of the outer two Galileans before going into orbit around Ganymede in late February 2028. There are hints in the presentation that JGO might attempt to encounter one of the outer irregular satellites during its mission.

The NASA-supplied component, JEO, would encounter Io four times during its mission. The first encounter would occur just before Jupiter Orbit Insertion (JOI), and like the flyby before Galileo's JOI, the Europa Orbiter would not acquire science during Io-0. During the other three encounters, performed in the second half of 2026, would all for 25% of Io's surface to be imaged at better than 200 meters/pixel. The last of the three encounters would occur at an altitude of 75 kilometers, enabling direct plume sampling, though the current sample profile would not allow for sampling of any known plume except for maybe the outer reaches of the Culann plume. It should be noted though that the tours shown are just examples that are subject to change. For example, the Cassini prime mission tour wasn't approved until a few years before it arrived at Saturn. The presentation goes on to mention that the radar instrument on JEO would be active for the flybys allowing for sub-surface sounding and altimetry. These could be useful in constraining tidal heating models and near-surface lithospheric structure. Another interesting slide in the EJSM presentation is the data return plan. The EJSM team plans to return 3 Gb per day from Jupiter during the tour, providing for hundreds of narrow angle camera images per day along with context images from other imagers. This could provide very decent monitoring of Jupiter and Io processes. Finally, the JEO team plans to image Io once or twice a week while in Europa orbit for monitoring purposes.

The payload for EJSM seems pretty capable. In addition to three camera systems (narrow-, wide-, and medium-angle cameras), the payload includes: a laser altimeter, an ice-penetrating radar, a Visible-IR spectrometer, an UV spectrometer, and Ion and Neutral Ion Spectrometer, a thermal instrument, a magnetometer, and a plasma and particle instrument. The communications antenna on JEO can also be used for radio science experiments. The specific instruments will be selected via an annoucement of opportunity. The JGO would carry a similar payload.

EJSM faces competition with TSSM for the Outer Planet Flagship Mission. TSSM would provide a NASA Titan orbiter, an ESA balloon, and an ESA lander planned for central Kraken Mare.

There is some disagreement between the presentations about when the downselection will occur. The EJSM presentations suggests that down-selection occurs in January 2009 with a confirmation of this selection by the ESA Science Programme Committee on February 4 (the ESA component would be formally approved at the end of 2012, where the component would have to compete with Xeus and LISA). A presentation by Curt Niebur still uses mid-February 2009 as the downselection date.

Sunday, November 9, 2008

Bruce Moomaw sent out the following e-mail with more information on the proposed Argo (Jupiter/Trojan)-Saturn-Neptune/Triton-Kuiper belt mission.

This is a follow-up by me to Emily's excellent piece on the "Argo" New Frontiers mission concept today ( http://www.planetary.org/blog/article/00001729/ ). It was inspired largely by the fact that -- in her original description of the mission last March ( http://www.lpi.usra.edu/opag/march_08_meeting/presentations/hammel.pdf ) -- Dr. Hammel emphasized the strong possibility that it might also fly by a Jovian Trojan on its way out to Saturn, rather than flying by Jupiter itself. (In fact, she described two possible missions of this sort on pg. 3 of her presentation.) These objects are looking more and more important scientifically, especially given both their rather puzzling origin and the fact that it now looks as though they total almost as much mass as the entire regular Asteroid Belt.

The question -- as with Alan Stern's similar "New Horizons 2", which would have flown by Uranus rather than Neptune on its way to a big KBO -- is whether such a mission would be worth the cost. On the other hand, "Argo" -- even without a Trojan flyby -- does include a very close flyby of Triton, which is a major item that "NH-2" didn't have.

Meanwhile, this summer's class of JPL Planetary Science Summer School devoted their yearly mission design effort this time to a possible Trojan-and-Centaur flyby:http://adsabs.harvard.edu/abs/2008DPS....40.1809S

(The Centaur 39P/Oterma [ http://en.wikipedia.org/wiki/39P/Oterma ] turns out to actually have an orbit between those of Jupiter and Saturn, suggesting that a mission to it could be solar-powered -- except for the danger that the solar panels would get machine-gunned by the particles in Oterma's coma.)

[Editorial note from Van: Bruce included Heidi Hammel’s complete reply in his e-mail. Since she sent the message to Bruce, I don’t want to reproduce it without permission. However she makes two interesting points: (1) the first Argo flyby can be either Jupiter or a Trojan, but Triton and a Kuiper belt object remain the priority and will dictate the trajectory flown; (2) even if another nation supplies an atmospheric probe for Neptune (or, by extension, Saturn) it would bust the Argo budget out of the New Frontiers cap.]

Saturday, November 8, 2008

Release Date: November 17, 2008The National Aeronautics and Space Administration (NASA) ScienceMission Directorate is releasing a Draft Announcement of Opportunity(AO) for community review and comment for the next mission in the NewFrontiers program (NNH09ZDA003J). The science objectives covered bythe Draft New Frontiers AO include South Pole -- Aitken Basin SampleReturn, Venus in Situ Explorer, Comet Surface Sample Return, NetworkScience, Trojan/Centaur Reconnaissance, Asteroid Rover/Sample Return,Io Observer, and Ganymede Observer. http://newfrontiers.larc.nasa.gov/

Note the opportunity to vote for your favorite mission on this blog page.

I've visited the website listed and the NSPIRES research opportunity webpage, and the AO draft apparently isn't up yet. Per http://newfrontiers.larc.nasa.gov/CommAnnouncement05122008.html the process and rules for the selection are:

o In August 2009, up to three missions will be selected for a 9 to 11 month Phase A that will be funded up to $2.5M each. Down selection to a single mission for flight will occur in fall (September to November) 2010. Launch is to occur no earlier than 2015 and no later than 2018.

o This NF-3 AO will solicit only missions that do not require nuclear sources for power generation or propulsion, although Radioisotope Heating Units (RHUs) and calibration sources will be allowed.

o The Principal Investigator (PI) Mission Cost for all phases of the mission will not include the launch vehicle and will be capped at $650M in FY09 dollars.

o Proposers will be given the option of selecting none or one of two specific technologies for insertion into their mission. The two technologies are the NASA Evolutionary Xenon Thruster (NEXT) and the Advanced Materials Bipropellant Rocket (AMBR) engine. For missions that insert NEXT, the cap on the PI Mission Cost will be raised up to $15M. For missions that insert AMBR, the cap on the PI Mission Cost will be raised up to $5M.

To refresh your memory, New Frontier’s missions are non-Mars (with a possible exception noted below) missions with a price tag of $500M-$1B. (The price envelope changes with each mission.) NASA announces that it will select a mission targeted to a pre-selected group of destinations, and scientists (paired with laboratories such as the Johns Hopkins Applied Physics Lab or JPL or paired with an aerospace company) propose missions. NASA then selects the mission with the best science return given the budget and development risk. The New Horizon’s Pluto mission was the first New Frontiers mission selected and the Juno Jupiter mission the second.

The price cap in particular seems very tight (although the launch is not included). My guess is that this will limit the complexity and development R&D of the missions. I expect that a fairly simple mission will be selected.

NASA preselects a group of target missions from which it selects the winning mission. (Mars has been excluded from previous selections.)

Which mission gets selected is hard to handicap in advance since it requires knowledge of the details of the proposals. Often issues of cost or risk not generally known to the public can be the deciding factor. Several of the targets have mission studies in progress as part of concept studies for the Discovery program but would use Stirling RTG power sources. I would not be surprised to see those proposals adapted for the New Horizons competition but with the use of solar panels.

It is fun to speculate about what you personally would like to see based on the thrill of exploration and expected scientific return. So for the next selection, here is my assessment; it is strictly personal and everyone is encouraged to present their own views:

Asteroid Rover/Sample Return – Returned samples can tell us much more than can a simple orbiter or lander. However, this mission probably has several challenges. The easy to reach near Earth asteroids probably are not the most interesting asteroids, and the main belt asteroids would be very challenging to do for a round trip mission. Grabbing the most scientifically meaningful sample from an asteroid is challenging. Also, laboratories have lots of asteroid samples already in the form of meteorites. Rovers on the small asteroids are technically challenging -- hoppers are easier. Rovers on larger main belt asteroids face the costs of reaching the destination and implementing a descent system.

Comet Surface Sample Return Mission – The New Frontiers competitions generally allow creativity in meeting the goals so an alternative mission that has been proposed to collect the samples from the coma might be an alternative. Here, I think that the diversity of comets and our new knowledge that they may have substantial dust covers makes it questionable whether or not a mission would get meaningful samples of the ice. I think this mission is unlikely to be chosen before the Rosetta comet rendezvous/lander mission tells us a lot more about the surfaces of comets. It would also be very challenging to return cryogenically frozen ice samples in a New Frontier’s budget. The review panels have said that it would be okay to propose a mission that returns melted samples, but the proposers would have to show that such samples would still have scientific merit.

Ganymede Observer/Io Observer – I put these together because they have similar challenges. The challenge for both these missions is to convince review panels that more flybys of these moons is a good way to spend $650M+. Based on past mission studies, an orbiter for Ganymede would not seem to fit within the budget (and is technically impossible for Io given the radiation). Both missions have the challenge of making solar panels work in the radiation belts of Jupiter (a much more severe challenge for an Io mission). I will point out that the two missions could be combined. A craft could initially do a series of Io flybys, raise perijove, and then do a series of Ganymede flybys (or alternatively, a series of Europa flybys) with continuing long range observations of Io and Jupiter. This more complicated mission probably busts the budget, but follow-on flybys of Ganymede might be funded as a Discovery program mission of opportunity. If the Jupiter system is selected as the target for the next flagship outer planets mission, then I don't either of these missions would be selected. If the Saturn system flagship mission is selected, then the appeal of a Jovian system may rise considerably.

Lunar South Pole-Aitken Basin Sample Return Mission – Sample return missions always rank highly in terms of scientific merit. This mission was a finalist for the last competition (losing out to Juno). Why it lost wasn’t clear based on scientific merit. The complexity of landing on the moon, selecting samples that answer the key scientific questions, and then returning to the Earth may have been too great.

Network Science (including Mars) for seismology and meteorological observations distributed across a globe (other observations also possible) – Mars is the obvious candidate. A network science mission is the second highest ranked scientific goal for Mars after a Mars Sample Return. However, this mission has been estimated to have a budget above $1B and it requires an orbiter to provide communications relay (not included in the >$1B estimate). Mars also already receives a substantial portion of NASA’s planetary science budget. My guess is that the next New Frontiers mission will be used to round out the list of targets NASA is exploring. ESA’s ExoMars 2016 mission also will include a single surface station that could teach us a lot about how to tune the instruments and design of a full network.

Trojan/Centaur Reconnaissance – These are an interesting series of targets, but I don’t know if NASA will be willing to use it’s ~2 times a decade chance to fly a New Frontiers mission to do reconnaissance.

Venus in Situ Explorer – A pair of short-lived Venus landers were proposed for the last New Frontiers competition. I’ve heard through the grapevine that the mission wasn’t selected because the timing was wrong to take advantage of alignments of planets for a launch within the budget timeframe. (There may also have been substantial mission cost and implementation risk – Venus’ surface is not a friendly place!) The exploration of Venus’ atmosphere in situ and surface has been ignored (by the next time a New Frontiers mission flies) for decades. Counting against this mission is the fact that the Venus scientific community is pushing for a much more ambitious mission to Venus involving an orbiter, balloons, and more capable landers. A mission using just balloons to explore the atmosphere could be an alternative.

So which missions would I like to see if every one could fit within the dollar and risk budgets? My first choice would be a pair of Venus landers. It simply has been too long since we’ve done in situ Venus science. If not that mission, I’d pick the Io Observer, partially because Io is my second favorite moon (after Titan) and because the mission can do additional Jovian system science (Jupiter meteorological observations, for example).

My choice for the following New Frontiers mission isn’t a competition at all. I’d go with the Argo Jupiter-Saturn-Neptune/Triton-Kuiper belt mission. While it would be flybys to at all destinations, the chance to take modern instruments to Neptune/Triton is compelling as is the opportunity to explore a wider variety of Kuiper belt objects than New Horizons can (post Pluto). Observing changes in the Jupiter and Saturn systems would simply be icing on the proverbial cake.

My guess is that the final selection will go for the mission with the lowest price tag and development risk that meets the minimum bar for scientific return. Don't get me wrong -- such a mission will produce excellent science, but it's public appeal may be limited. I think the selection of the Discovery Grail mission in the last selection is an example of this criteria in operation. Superb science, but not exciting exploration. That, I think, is the price future missions will pay for past successes (all the cheap, exciting exploration missions have been done) and mistakes (the cost overruns on the Mars Science Laboratory, James Webb telescope, Kepler mission, etc.).

Emily Lakdawalla of the Planetary Society has posted an excellent blog entry on a proposed Neptune flyby mission, Argo, that would also flyby Jupiter, Saturn, and one or two medium sized Kuiper belt worlds.

http://www.planetary.org/blog/article/00001729/

If you don't follow Emily's blog, take a look at it. The posts are always excellent -- thoughtful and knowledgeable.

Thursday, November 6, 2008

I’ve skimmed through the Fall 2008 American Geophysical Union abstracts for those that provide enough information on proposed future missions to be interesting standalone documents. (Often the abstracts for future missions discuss what will be talked about rather than providing details.) You can peruse the entire planetary portion of the meeting at: http://www.agu.org/cgi-bin/sessions5?meeting=fm08&sec=P. Presentation numbers for each of the abstracts is given so you can look up authors, etc., from the full abstract.

I will be attending the conference, but for my primary field, the remote sensing of vegetation structure. I’ll attend as many of the planetary sessions as possible, but this is a huge conference and only a tiny fraction of presentations in any field can be attended.

P33A-1439TI: Nuclear Polar VALOR: An ASRG-Enabled Venus Balloon Mission ConceptAB: In situ exploration of Venus is expected to answer high priority science questions about the planet's origin, evolution, chemistry, and dynamics as identified in the NRC Decadal Survey and in the VEXAG White Paper. Furthermore, exploration of the polar regions of Venus is key to understanding its climate and global circulation, as well as providing insight into the circulation, chemistry, and climatological processes on Earth. In this paper we discuss our proposed Nuclear Polar VALOR mission, which would target one of the polar regions of Venus, while building on design heritage from the Discovery class VALOR concept, proposed in 2004 and 2006. Riding the strong zonal winds at 55 km altitude and drifting poleward from mid-latitude this balloon-borne aerial science station (aerostat) would circumnavigate the planet multiple times over its one- month operation, extensively investigating polar dynamics, meteorology, and chemistry. Rising and descending over 1 km altitude in planetary waves - similar to the two VEGA balloons in 1985 - onboard instrumentation would accurately and constantly sample and measure other meteorological and chemical parameters, such as atmospheric temperature and pressure, cloud particle sizes and their local column abundances, the vertical wind component, and the chemical composition of cloud-forming trace gases. As well, when viewed with terrestrial radio telescopes on the Earth-facing side of Venus, both zonal and meridional winds would be measured to high accuracy (better than 10 cm/sec averaged over an hour). Due to three factors: the lack of sunlight near the poles; severe limitations on the floating mass-fraction available for a power source; and the science requirements for intensive and continuous measurements of the balloon's environment and movement, a long-duration polar balloon mission would require a long-lived internal power source in a relatively lightweight package. For our concept we assumed an Advanced Stirling Radioisotope Generator (ASRG). In return, this mission would provide two orders of magnitude more science data than expected from the original battery-powered VALOR concept, and could reduce measurement uncertainties by a factor of five. In addition to the science return, the secondary objective of this proposed mission would be to space qualify ASRGs through all mission phases and in various operating environments. Lifetime testing would be demonstrated using a second ASRG on the carrier that would keep operating after the in-situ element is delivered. Based on the results of this and another eight ongoing NASA funded studies, NASA will make a decision about the inclusion of ASRGs in the next Discovery AO, due in the summer of 2009.

P21A-1346TI: The Titan Saturn System MissionAB: A mission to return to Titan after Cassini-Huygens is a high priority for exploration. Recent Cassini-Huygens discoveries have revolutionized our understanding of the Titan system, rich in organics, containing a vast subsurface ocean of liquid water, surface repositories of organic compounds, and having the energy sources necessary to drive chemical evolution. With these recent discoveries, interest in Titan as the next scientific target in the outer Solar System is strongly reinforced. Cassini's discovery of active geysers on Enceladus adds an important second target in the Saturn system.The mission concept consists of a NASA-provided orbiter and an ESA-provided probe/lander and a Montgolfiere. The mission would launch on an Atlas 551 around 2020, travelling to Saturn on an SEP gravity assist trajectory, and reaching Saturn about 9.5 years later. The flight system would go into orbit around Saturn for about 2 years. During the first Titan flyby, the orbiter would release the lander to target a large northern polar sea, Kraken Mare, and the balloon system to a mid latitude region.During the tour phase, TSSM will perform Saturn system and Enceladus science, with at least 5 Enceladus flybys. Instruments aboard the orbiter will map Titan's surface at 50 m resolution in the 5 micron window, provide a global data set of topography and sound the immediate subsurface, sample complex organics, provide detailed observations of the atmosphere, and quantify the interaction of Titan with the Saturn magnetosphere. A subset of the instruments would provide spectra, imaging, plume sampling and particles and fields data on Enceladus. Instruments aboard the balloon will acquire high resolution vistas of the surface of Titan as the balloon cruises at 10 km altitude, as well as make compositional measurements of the surface, detailed sounding of crustal layering, and chemical measurements of aerosols. A magnetometer, will permit sensitive detection of induced or intrinsic fields. The probe/lander will splash into a large northern sea and spend several hours floating during which direct chemical and physical sampling of the liquid would be undertaken. During its descent the probe would provide the first in situ profiling of the winter northern hemispheric atmosphere, distinctly different from the equatorial atmosphere where Huygens descended and the balloon will arrive. Radio science experiments should be capable of providing detailed information on Titan's tidal response, and hence its crustal rigidity and thickness.

N: P21A-1347TI: Cassini Radar: Extended Mission Plans and Expected ResultsAB: Cassini completed its four year Prime Mission in July, 2008. This included a total of 45 close Titan flybys, with radar data obtained on 23 of these. An approved two year extended mission will provide an additional 25 close Titan flybys, with radar data collected on 12 of these. The prime mission radar data covered primarily the northern hemisphere of Titan, and the priority for the extended mission radar observations will be to fill in southern hemisphere coverage and provide limited repeat coverage for change detection in the north. During the prime mission, all but one flyby included some form of synthetic aperture imaging, leading to a wide range of viewing geometries. Imaging resolution varied from 300-500 m at the closest approach altitudes (1000 km) to about 2 km during high altitude (20,000 km) imaging segments. Altimetry, scatterometry, and radiometry mode data were also collected over multiple geometries to sample Titan's scattering and emission functions. The varying geometry and instrument parameters, which lead to varying resolution, SNR, polarization, incidence angle and noise characteristics, must be properly accounted for when interpreting these data. Here we review the coverage and other important characteristics of the radar data sets obtained at Titan in the prime mission, and compare these with plans for the extended mission. The first extended mission radar observation will occur on Dec 5, 2008, and we will present these timely preliminary results if the spacecraft operates as planned. Prime mission data along with corresponding surface coverage from ISS and VIMS have revealed a diverse Titan surface, which will be further augmented and analyzed by extended mission results. This work is supported by the NASA Cassini Program at JPL - Caltech.

AN: P22A-08TI: A Venus Flagship Mission: Exploring a World of ContrastsAB: Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission to Venus. This 3- to 4 billon mission, to launch in the post 2020 timeframe, should revolutionize our understanding of how climate works on terrestrial planets, including the close relationship between volcanism, tectonism, the interior, and the atmosphere. It would also more clearly elucidate the geologic history of Venus, including the existence and persistence of an ancient ocean. Achieving these objectives will provide a basis to understand the habitability of extra solar terrestrial planets. To address a broad range of science questions this mission will be composed of flight elements that include an orbiter that is highlighted by an interferometric SAR to provide surface topographic and image information at scales one to two orders of magnitude greater than that achieved by any previous spacecraft to Venus. Two balloons with a projected lifetime of weeks will probe the structure and dynamics of the atmosphere at an altitude of 50 to 70-km. In addition, two descent probes will collect data synergistic to that from the balloon and analyze the geochemistry of surface rocks over a period of hours.

The abstracts themselves are now available ( http://www.agu.org/cgi-bin/sessions5?meeting=fm08&sec=P ), and I've gone through them looking for things that might interest you -- or at least, they interested me. There are a few genuine lulus, which I'll leave you the pleasure of picking out from the following list of abstracts on various subjects that I found interesting.

Mars (general): P41B-1365; P41B-1373; P44A-02

Early Mars habitability: P43D-01; P43D-02; P44C-05; P53B-1455

Phoenix: P13F-01 (Some new information is in the abstract itself!)

Mars carbonates (and how they may have coexisted with the sulfates): P31D-05; P43D-05; P43B-1392; P43B-1396;

Titan: P11D-01; P11D-06; P11D-04 (new surface composition candidate); P21A-1313 and P52A-03 (the last two are connected in a big way)

Iapetus: P31C-08

Pluto: P51C-1425

Early Earth: P33D-01; P33D-02

Extrasolar planets: P13C-1327; P13C-1332; P13C-1333; P33D-08

Spacecraft design: P33A-1439; P51C-1426; P53C-1471

There are also three more that link up with Chris McKay's recorded 49-minute Oct. 6 talk on the astrobiological significance of the Phoenix findings -- which is very good, although with the caution that it runs 110 Mbytes: http://www.youtube.com/watch?v=1plIgTG9x-A . I may summarize his conclusions later on for those who don't want to go to that much download trouble -- but in any case, the relevant AGU abstracts are:

P11A-1235; P41A-1347; P51B-1417.

Actually, let me go ahead and name the other abstracts that really jumped out at me. Besides those regarding Enceladus' possible ocean salts, take a look at the Titan abstracts (especially the two connected ones); those on Saturn's rings and Iapetus (the latter turns out to have an entirely new major surprise for us); and the one on the possible recent origin of Europa's ocean. The abstracts taking varying views of the possible habitability of Noachian-era Mars also make a nice set.

Space.com has an article on the possible ESA Titan balloon contribution to a Flagship Titan Saturn System mission http://www.space.com/scienceastronomy/081106-am-titan-balloon.html.

The article states that the balloon gondola will have the ability to float and lakes while the mission will have the ability to grab and then analyze surface samples. This would be great if it's true, but I have my doubts. While it is easy to have a balloon descend to the surface, it is much harder to prevent damage to the gondola and balloon if winds drag them across the surface. Perhaps this is some kind of snake that would be tolerant of dragging across the surface that would be lowered to the surface to grab samples.

These low ground maneuvers would be that much harder to manage with Titan a long distance away (I forget how long it takes a radio wave to travel the distance) and the orbiter only occasionally in direct contact with the balloon (even when the orbiter has reached Titan orbit).

Anyone know anything more about this?

On the bummer side, the TSSM mission would arrive in the Saturn system in 2030. That would make me only 74 on arrive and about 76 when it finally reaches Titan orbit. Whichever flagship destination is chosen (Titan or Europa), this will be my last outer planet flagship mission. I suddenly feel a lot older...

Wednesday, November 5, 2008

In a previous post, I discussed possible options for NASA Mars missions following the Mars Science Lab (MSL) and the Scout Maven upper atmosphere mission for 2013. In this post, I will discuss current thinking about a follow on rover mission.

There are three explicit goals for a next generation Mars rover:

o Launch within 6 to 8 years of MSL to keep the rover development team intact. This would require a launch by 2016 if MSL holds to its current 2009 launch.o Explore a new type of Mars terrain that has an apparent history of an aqueous environment and therefore a possible past site of biological activity. The flotilla of Mars orbiters has identified at least 8 types of terrain with aqueous history. Opportunity is exploring one type, MSL will explore another, and hopefully ExoMars will explore a third. A 2016 rover would target yet another. o Collect and cache a sample suite that could be retrieved by a future sample return mission.

And one implicit goal:

o Fall in price between MER ($820M for two rovers (equivalent to ~$1.2B in 2016 dollars at 3%/year inflation)) and MSL (>$2B). A February 2008 cost estimate for the 2016 mission was $1.6B (although it wasn’t stated whether that was 2008 or 2016 dollars).

The 2016 rover would be larger than the MER rovers (~250kg vs 174kg) with ~11kg of instruments (vs 4.5kg for MER) plus the sample collection and caching system. A precision landing capability would require a landing system similar to MSL’s skycrane. Using solar power would reduce costs compared to MSL nuclear power system. Funding the development of the 2016 is stated to be difficult within projected budgets for that launch opportunity.

The current rover concept looks like MER, probably to emphasize its modest goals compared to MSL (I expect that the final design will be different than both).

A straw man science payload would be an expanded set of MER instruments. An alpha-proton-x-ray spectrometer would identify rock and soil elements. A near infrared (NIR) spectrometer replace’s MER’s mini thermal emission spectrometer (mini-TES) for remote mineral identification. A second NIR would work in conjunction with the microscopic imager for close up mineral identification. A Raman spectrometer would identify minerals, including those bearing carbon molecules. The sample cache system could be able to cache 20 rock cores and 3 regolith samples.

So far, this post has reported on the current thinking presented at Mars Exploration Program Analysis Group (MEPAG) meeting. What follows are my editorial comments. As currently envisioned, the 2016 rover would be a one of a kind mission flown in only one launch opportunity, like MER (but with two rovers) and MSL. I personally disagree with this plan. Designing and testing each rover and entry and landing system is an expensive proposition. Given limited Mars program funds, I think that flying one off mission designs is sub optimal. The Mars program has reused its orbiter designs across multiple missions. So far, though, the apparent reuse of rover design between missions has been much more limited.

In my opinion, the Mars program after 2013 should focus on exploring the diversity of Mars surface terrains. The 2016 opportunity should be used to fly the Mars Science Orbiter (MSO). This orbiter would study trace gases in the Martian atmosphere and continue climate studies. Most importantly for future rover missions, this orbiter could also carry a new high resolution camera to examine landing sites and enable traverse planning as well as act as a communications relay.

The next several Mars launch opportunities would then fly identical copies of the new rover design to study a variety of Martian terrains. This approach amortizes the high cost of the initial design and testing across multiple flights. It also gives us ground truth at multiple sites and ready to retrieve sample caches from a diversity of sites. Landing sites could either be selected by the whole community as done for MER and MSL, or principle investigators could compete with proposals to fly to particular locations.

There are issues with my proposal. The later flight date for the first rover flight creates a long delay after the MSL design (and hopefully its launch) making it hard to keep the design team together. Improvements in technology would make it impractical to refly the same design too many times (although subsystems could be enhanced between launches). Two to four launch opportunities (~4-8 years) seems to be the maximum practical before a redesign to make use of new technologies makes more sense than reusing an existing design. Another issue is that this roadmap has no place for a Mars network mission, which has the second highest science priority after a Mars sample return. One solution would be to fly the network mission in 2018 and delay the rover mission to 2020, although this exacerbates the problem of keeping the rover team intact. Another solution would be for another nation to fly the network stations with NASA providing communications relay with MSO.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.